meson: remove dri-search-path

It's not actually used anywhere.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31223>

meson_options.txt

@@ -66,14 +66,6 @@ option(
                 'Do not enable unless you know what you are doing. Default: false'
 )
 
-option(
-  'dri-search-path',
-  type : 'string',
-  value : '',
-  description : 'Locations to search for dri drivers, passed as colon ' +
-                'separated list. Default: dri-drivers-path.'
-)
-
 option(
   'expat',
   type : 'feature',